Erosion-corrosion resistant aluminum radiator clad tubing

ABSTRACT

A composite aluminum article having increased resistance to erosion corrosion in aqueous environments comprising an aluminum base alloy cladding consisting essentially of 0.8 to 1.3% zinc, 0.7% maximum silicon plus iron, 0.10% maximum copper, 0.10% maximum manganese, 0.10% maximum magnesium, balance essentially aluminum, bonded to at least one side of an aluminum base alloy core consisting essentially of manganese from 1.0 to 1.5% chromium from 0.1 to 0.4% copper from 0.05 to 0.4%, balance essentially aluminum.

United States Patent Anthony et al. 1 Jan. 7, 1975 EROSION-CORROSION RESISTANT 3,480,411 11/1969 Pryor 29/191 LUMI RADIATOR CLAD TUBING 3,649,227 3/1972 Fetzer et aL. 29/197.5

[75] Inventors: William H. Anthony; James M. FOREIGN PATENTS 0R APPLICATIONS Popplewell, both of Guilford, Conn. 1,390,907 1/1965 France 29/1975 73 Assi nee: Olin Cor oratio N H 1 g Corm p ew aven Primary Examiner-A. B. Curtls Attorney, Agent, or FirmRobert H. Bachman [22] F1led: Feb. 4, 1974 [21] Appl. N0.: 439,336 [57] ABSTRACT Related Application Data A composite aluminum article having increased resis- [62] Division of Ser No 222 795 Feb 2 1972 Pat No tance to erosion corrosion in aqueous environments 3 809 comprising an aluminum base alloy cladding consisting essentially of 0.8 to 1.3% zinc, 0.7% maximum sili- 52 U.S. c1 29/191 29/197.5 010% maximum COPPER 010% 51 Int. Cl 13321 15/00 mum manganese 010% maximum magnesium [581 Field of Search 29/191 197.5 essentia'ly aluminum bonded to at 63810116 Side of an aluminum base alloy core consisting essentially [56] References Cited of manganese from 1.0 to 1.5% chromium from 0.1 to 0.4% copper from 0.05 to 0.4%, balance essentially UNITED STATES PATENTS aluminum. 2,726,436 12/1955 Champion 29/197.s 3,133,796 5/1964 Craig, Jr. 29/197.5 4 Claims, 2 Drawing gures EROSION-CORROSION RESISTANT ALUMINUM RADIATOR CLAD TUBING This is a division of application Ser. No. 222,795, filed Feb. 2, 1972, now US. Pat. No. 3,809,155.

BACKGROUND OF THE INVENTION It is highly desirable to develop composite aluminum articles having improved resistance to erosion corrosion in aqueous environments due to the wide use of aluminum commercially in aqueous environments.

For example, aluminum tubing which is used in heat exchangers such as aluminum radiators should have high resistance to erosion corrosion damage by the aqueous heat exchange fluid.

Aluminum automobile radiators have been extensively tested. Unfortunately, however, materials which are suitable are often subject to corrosion damage and, hence, have a limited life expectancy due to the development of leaks in service. The leaks may be developed due to the erosion corrosion channeling excavating the tube wall as the coolant stream passes around blockages in the tubes. Very high stream velocities which could occur in such channels can readily result in erosion corrosion damage unless the material is highly resistant to this type of damage.

Accordingly, it is an object of the present invention to provide composite aluminum articles having improved resistance to erosion corrosion in aqueous environments.

It is a further object of the present invention to provide composite aluminum tubing having improved resistance to erosion corrosion in aqueous environments.

It is a still further object of the present invention to provide an improved heat exchange assembly utilizing said tubing, a process for improving heat transfer with resistance to erosion corrosion in an aqueous environment and an improved heat transfer system.

Further objects and advantages of the present invention will appear from the ensuing specification.

SUMMARY OF THE INVENTION In accordance with the present invention it has now been found that the foregoing objects and advantages may be readily achieved.

Composite aluminum articles of the present invention have substantially improved resistance to erosion corrosion in an aqueous environment. The composite comprises an aluminum alloy cladding consisting essentially of 0.8 to 1.3% zinc and 0.7% maximum silicon plus iron, 0.10% maximum copper, 0.10% maximum manganese, 0.10% maximum magnesium, balance essentially aluminum bonded to at least one side of an aluminum base alloy core consisting essentially of manganese from 1.0 to 1.5%, chromium from 0.1 to 0.4%, copper from 0.05 to 0.4%, and the balance essentially aluminum.

The present invention also contemplates a composite aluminum tubing and a high strength heat exchange assembly having improved resistance to erosion corrosion in an aqueous environment. The assembly comprises at least one header connected by at least one tube and a secondary heat exchange surface connected to said tube. The tube is the improved composite aluminum tubing of the present invention. The preferred embodiment includes two parallel headers connected by a plurality of said tubes perpendicular therewith, with corrugated fin stock material being bonded to said tubes.

The present invention also contemplates an improved heat transfer system and a process for providing heat transfer with resistance to erosion corrosion in an aqueous environment. The process comprises providing the metal tubing of the present invention having entrance and exits ends, affixing said entrance and exit ends to two tube sheets, passing a first aqueous liquid through said tubing and contacting the external surface of the tubing with a second fluid in heat exchange relationship with the first fluid.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of the present invention.

FIG. II is a front view, with portions cut away, of an automobile radiator including the tubing of the present invention.

DETAILED DESCRIPTION The composite aluminum articles of the present invention comprises an aluminum alloy cladding consisting essentially of 0.8 to 1.3% zinc and 0.7% maximum silicon plusiron, 0.10% maximum copper, 0.10% maximum manganese, 0.10% maximum magnesium, balance essentially aluminum bonded to at least one side of an aluminum base alloy core consisting essentially of manganese from 1.0 to 1.5%, chromium from 0.1 to 0.4%, copper from 0.05 to 0.4%, and the balance essentially aluminum.

As indicated hereinabove, the present invention is characterized by surprising resistance to erosion corrosion in an aqueous environment wherein the aluminum alloy cladding is exposed to the aqueous environment. It has also been found that this improved resistance can be accomplished with retention of excellent physical properties.

In addition to the foregoing, the composite of the present invention has improved resistance to pitting corrosion.

The excellent erosion corrosion resistance of the composite of the present invention is highly desirable commercially. This property admirably lends the tubing of the present invention to use in heat exchange assembly such as in an aluminum radiator and the tubing of the present invention would result in a substantially longer useful life. The surprising properties achieved in accordance with the present invention would give the material of the present invention good utility in other applications using high speed fluids.

It has been found that in aqueous environments wherein erosion corrosion or impingement attack occurs, as for example, upon the inside wall or cladding 2, as shown in FIG. I of the tubing carrying the aqueous solution, that the aluminum composite of the present invention has surprising resistance to this destructive attack. This resistance is obtained since, should perforation of the aluminum alloy cladding 2, as shown in FIG. 1, occur, further localized corrosion is retarded or eliminated by the cathodic protection afforded to the exposed alloy core 4. More specifically the cladding material is anodic to the core material in an aqueous environment such as an antifreeze solution in automotive radiators and should localized perforation of the cladding occur, as in impingement attack, the current generated by the relatively large anode and small cathode is such as to effectively inhibit penetration of the core and hence the core is cathodically protected from further attack.

The cladding material of the present invention may also contain impurities such as up to 0.7% silicon plus The aluminum radiator may be prepared in a conventional manner utilizing brazing in a continuous aluminum radiator manufacturing line. As a specific example, an aluminum radiator may be prepared from tubiron, up to 0.1% copper, up to 0.1% manganese, up to 5 ing of the present invention having a 17 mil thick wall 0.1% magnesium, others 0.05% each, total 015%, and fin stock which may be either the same alloy as the The core material of the present inv tion may l core material or a conventional aluminum alloy of the contain impurities such as up to 0.6% silicon, up to 4XXX Series for p alumihum alloy 4043, 4343 0.7% iron, up to 0.1% zinc and others 0.05% each, total or 4045. An assembly is prepared having the configura- 0.l5%. tion of the desired aluminum radiator. The fixtured as- Naturally the cladding may be bonded to the outside sembly is dip coated with a salt flux and then furnace f e f th core h ld h aqueous di flo brazed in a continuous manner on a production line. around the tubes rather than through them or the core The radiators P through ah thrhaee ,Where the may advantageously be clad on both Sid wh r i a brazing filler metal melts and then solidifies resulting in first aqueous medium passes through the tubing and a the formation of a rigid assembly. Alternatively, fluxsecond aqueous medium passes around the tubing. leSS brazing P eS m y e used- Th bi of h present invention normally, but not As aforementioned an additional cladding of a braz necessarily has a wall thickness no-larger than 0.10 ihg alloy Such as an AA 4XXX Series alloy y be i h wh h bi of the present invention is used bonded to the exposed surface of the core material for in a high strength aluminum radiator, the tubing has a bonding to the fin Stock, if desiredwall thickness 0.030 inch or smaller and perferably has Thus, in accordance with the present invention the a wall thickness from 0.010 inch to 0.020 inch. For g strength heat exchange assembly y have the heat exchange applications in general, the tubing of the configuration Shown in H, which represents ah present invention most advantageously has a wall thicklustl'ative heat exchanger embodhheht- Referring how ness f 1 i h d ll to FIG. II, the radiator assembly includes a heat dissi- The percentage thickness of the cladding of the tub- P g or core 6 having at pp ends a P tahk ing of the present invention is not critical but generally of inlet header 8 and bottom k of Outlet header t ranges from 5 to 25% of the total composite wall thickadapted eohheetloh; P Y y Wlth the e ness of the composite in order to insure a sufficient e and Intake eohdults e a eyhhder bloek eoehhg thickness of the core material for strength as well as Jacket for the flow of coohhg aqueous medum from sufficient thickness of the cladding in order to provide one tank t the Otheh The eore 6 15 made p of a for a sufficiently long cladding life in service. ber of fluld passageways of water tubes 12 of the pres- The tubing of the present invention may be Ieadlly ent mvention. The tubes are spaced apart by fin str1ps prepared by conventional methods For example, 14. The fins are folded or corrugated between tubes 12 mlnum ingots may be conventionally prepared and andextend between ad acent walls or ad oining tubes rolled to Strip in a conventional manner and then strlps to divide the space into a number of relatively small air of the clad and core material rolled together. The matecells rial may then be welded or extruded into tubing having The present mvemlon be m ore readlly apparem the desired configuration. The tubing may also be from a consideration of the following illustrative examformed by drawing of the core in tubular form over the 40 p165 cladding material in tubular form if desired. EXAMPLE l If desired fins of an alloy such as the AA 4XXX series Y r a a or of the core material may be provided on an exposed Three alloys, Alloys A, Band C, were Durville cast surface of the core material and bonded thereto by, for and then homogenized at l,125 F for about 8 hours example a brazing filler metal or by providing an addiand air cooled. The composition of the resulting alloys tional cladding bondedto the core which is suitable for is shown in Table I below:

TABLE I Composition lngot Si Fe Cu Mn Mg Cr Zn Ti A .21 .41 .11 1.18 .11 .005 B .19 .35 .20 H8 .21 .11 .007 c .03 .24 1.03 .005

bonding to the fin material, such as an AA 4XXX series EXAMPLE H Y lngots A and B of Example I were scapled to 1.5

Rafhator tubmg generally seam welded inches and then wire brushed and vapor degreascd. stantlally round tubmg and flattened into an oval or flat Ingot C was hot rolled at 00 F to 025 inch gage using cross sectlon. Thus, bonding together of the clad and a 1 inch pass-with reheating to 00 F with each core material may be readily achieved y rolling of the 0nd pass. The hot rolled material was then cold rolled composites together .before welding. The smaller dito 0,050 i h g g Th 0,050 i h gage i l f mension is preferably from 0.05 to 0.2 inch. The larger i t C was th n welded t ach of th A and B i t dimension is preferably from 0.3 to 1.2inches. For heat slabs on four sides to form A and B composites'respecexchange applications in general, the tubing of the tively leaving 1 inch long openings in the weld across present invention may be advantageously used having an outside diameter (O.D.) up to several inches and preferably from )4 inch 0D. to 2 inches O.D.

one of the shorter edges so that air could be expelled during further rolling of the composites. The composites were then heated to 800 F for 5 minutes and given skin passes of about a 3% reduction each with the partially opened edge facing in a direction opposite to the travel of the composites. The composites were then reheated to 800 F, hot rolled to 0.25 inch gage, and then control A composite.

EXAMPLE IV The present example illustrates the potential differcold rolled to @050 inch gage- 5 ence between the alloys of the composite of the present The cladding thickness of the A and B composites invention. were then measured on mounted and polished sections Durville ingots of the following composition were and found to be 1.5 and 1.6 mils thick respectively. cast and homogenized and processed to .050 inch gage The composites of Example I were then heated up as in Example I and then subjected to a simulated and cooled down using a pit furnace such a way to brazed condition as in Example II.

TABLE II lngot Si Fe Cu Mn Mg Cr Zn Ti simulate the effect of a brazing step in a continuous alu- Specimens were cut from the A and B alloys and minum radiator manufacturing line. This was done in from .050 inch gage C cladding material of Example I order to allow for any possible interdiffusion effects for impingement testing as in Example III. A portion of which could result in reducing the electrode potential each pecimen was passed through a special composite difference between the compo t of h composite gasket of silicon rubber in the jet chamber of the jet tesduring the alumi m di t f t i Th h ter without making electrical contact with the flange or up and cool down cycle is as follows: The composites laaklhg y ahtlffaele when the gasket was tlghtehed were heated to 1,150 P and cooled to 800 F within 2 ,25 Special rubber inserts were p y so that the p minutes at a constant cooling rate and then quenched mehs weta mounted Without incurring y electrical i water at 1 0 F leakage to the stainless steel jet tester chamber. In this manner it was possible to mount dissimilar specimens EXAMPLE in jet test chambers and measure the current flow be- The Composites f Example I and I] were cut into tween them wh1le they were sub ected to antifreeze et propriate s ze specimens and subjected to impingement iPl l atflany temperature g g h by a plurality of ets of an aqueous ant freeze material 6 1 3 0W '5 l l f hf g g t j h fi g- 15 313 ,j;j 212 3336521352??? n; TaiEZ'ZFIJZ 55815531251282 tomo a t moste t r g g zz t? pgocgssing g 1 5 gi 2 than .5% of the total electrolytic resistance path in the thickness in'Example I and the composite A were antifreeze between the two test specimens. In this manployed as controls. The antifreeze material was a comthe current flow between Alloy C of Example I and Alloy A of the present example and Alloy C of Example mercial, inhibited aqueous ethylene glycol containing I and Alloy B of the present example was monitored a 45% nominal by volume ethylene glycol whlch was wh1le the antifreeze impinged on the samples at 98 feet due cted onto the samples at a temperature of about 40 p Second The temperature was cycled p and down 200 a the veloclty 2 98 feet per from 40 to 105 C for three successive cycles. The disecAon i g out d rection of current flow throughout the cycling was such t 6 6 test t e Speclmens were remiwe that the alloy C of Example I component remained anand rlnsed in distilled water followed by solvent rinses Odie for both.couples m mfathanol and benzjene sampl es were It was apparent that throughout the several cycles the chemlcany Cleaned by "nmerslhg h m aqueous current output of the Alloy BAlloy C was about five bath of P P Ph actds at 80 They times as great as the Alloy A-Alloy C. Thus a startling were then rinsed n distilled water, dried and the depths nd unexpectedly large difference to the protective caof the resultant lmplhgemeht ctatets h t The thodic current is provided by the Alloy C anode matedepth of attack the Control hompfislte comprlslhg the rial coupled to Alloy B and this is especially true within A P C material composlte A and the pq the temperature range of 90 to 105 C where automoited alloy A matenal was found to be about 3 "h biles normally operate. In particular the Alloy A-Alloy whereas the depth of attack in the composite compris- C couple id d 16 micmamps Current in the ing the B and C material Or composite B was fo I0 scending leg of the third cycle at a temperature of 93.3 be about 1.8 mils maximum. The exposed core of the C (or 200 F) while the Alloy B-Alloy C couple pro- B composite or the B alloy was found to be substanvided I00 microamps at the same point. ttally free of attack attesting to the lgaivflll'llgdpl'oteitlfin Thlsdmvention hmay be emblimdieddm other forms tor afforded to the B alloy by the C al 0y c a ing 0 t e carrie out in ot er ways wit out epartmg rom t e composite whereas the exposed core material of the A spirit or essential characteristics thereof. The present composite or the A alloy had numerous small pits indiembod ment is therefore to be considered as in all recating that the galvanic protection afforded to the alloy P a a Testrlatlve, the SCORC 0f the by the C alloy cladding is practically nonexistant. lnventloh belhg Indicated hy t PP a Claims, and

The cladding adjacent to the exposed core of the B f chahgtlts whlch i c i l a i d t l l range composite was found to be substantially consumed 0 eqthva are late 8 to e em race etelh' thereby indicating cathodic protection was provided to the B alloy core whereas there was substantially less consumption of the cladding in the crater rim of the What is claimed is: l. A composite metal article having improved resistance to erosion corrosion in aqueous environments said core.

3. A composite metal article according to claim 1 wherein said cladding contains up to 0.7% silicon plus iron, up to 0.1% copper, up to 0.1% manganese, up to 0.1% magnesium, others 0.05% each, total 0.15%.

4. A composite metal article according to claim 1 wherein said core contains up to 0.6% silicon, up to 0.7% iron, up to 0.1% zinc, and others 0.05% each, total 0.15%.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 59, 59 Dated January 7, 975

Inventor(s) William H. Anthony et a1,

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Page 1, in the heading, after the word "Assigneez" insert --Swiss Aluminium Ltd. Chippis, Sw1tzerland---.

Column 1, line 18, afterthe words "subject to" insert ---erosion---.

Column 6, line 33, the word "aross" should read ---across---.

Signed and sealed this 1st day of April 1975.

(SEAL) Attes-t: h C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Arresting Officer and Trademarks 

1. A COMPOSITE METAL ARTICLE HAVING IMPROVED RESISTANCE TO EROSION CORROSION IN AQUIOUS ENVIROMENTS COMPRISING AN ALUMINUM.BASE ALLOY CLADDING CONSISTING ESSENTIALLY TO 0.8 TO 1.3% ZINC, 0.10% MAXIMUN SILICON PLUS IRON,0.10% MAXIMUN COPPER, 0.10% MAXIMUN MAGANESE, 0.10% MAXIMUN MAGNESIUM, BALANCE ESSENTIALLY ALUMINUN BONDED TO AT LEAST ONE SIDE OF AN ALUMINUM BASE ALLOY CORE CONSISTING ESENTIALLY OF MAGANESE FROM 1.0 TO 1.5% CHROMIUM FROM 0.1 TO 0.4% COPPER FROM 0.05 TO 0.4%, BALANCE ESSENTIALLY ALUMINIM.
 2. A composite metal article according to claim 1 wherein said cladding is bonded to opposing sides of said core.
 3. A composite metal article according to claim 1 wherein said cladding contains up to 0.7% silicon plus iron, up to 0.1% copper, up to 0.1% manganese, up to 0.1% magnesium, others 0.05% each, total 0.15%.
 4. A composite metal article according to claim 1 wherein said core contains up to 0.6% silicon, up to 0.7% iron, up to 0.1% zinc, and others 0.05% each, total 0.15%. 